Hard disk drives are used in almost all computer system operations. In fact, most computing systems are not operational without some type of hard disk drive to store the most basic computing information such as the boot operation, the operating system, the applications, and the like. In general, the hard disk drive is a device which may or may not be removable, but without which the computing system will generally not operate.
The basic hard disk drive model was established approximately 50 years ago and resembles a phonograph. That is, the hard drive model includes a hard storage disk that spins at a standard rotational speed. An actuator moves a magnetic read/write head over the disk. The actuator arm carries a head gimbal assembly (HGA) that includes a slider and a suspension with a nose portion for directly contacting a ramp used during the load and unload cycles for a load/unload drive. The slider carries a head assembly that includes a magnetic read/write transducer or head for reading/writing information to or from any desired location on the disk.
In operation, the hard disk is rotated at a set speed via a spindle motor assembly having a central drive hub. Additionally, there are tracks evenly spaced at known intervals across the disk. When a request for a read of a specific portion or track is received, the hard disk aligns the head, via the arm, over the specific track location and the head reads the information from the disk. In the same manner, when a request for a write of a specific portion or track is received, the hard disk aligns the head, via the arm, over the specific track location and the head writes the information to the disk.
Over the years, the disk and the head have undergone great reductions in their size. Much of the refinement has been driven by consumer demand for smaller and more portable hard drives such as those used in personal digital assistants (PDAs), MP3 players, and the like. For example, the original hard disk drive had a disk diameter of 24 inches. Modern hard disk drives are much smaller and include disk diameters 3.5 to 1 inches (and even smaller 0.8 inch). Advances in magnetic recording are also primary reasons for the reduction in size.
However, the decreased track spacing and the overall reduction in HDD component size and weight in collusion with the load/unload drive capabilities have resulted in problems with respect to the HGA in general and the slider suspension in particular. Specifically, as the component sizes shrink, a need for tighter aerial density arises. In other words, the HGA is brought physically closer to the magnetic media. In some cases, the HGA will reach “ground zero” or contact recording. However, one of the major problems with near contact recording is the effect of vibration resonance when a slider encounters the asperities of the magnetic media or disk.
For example, when the slider contacts the disk, dynamic coupling between the slider and components of the head gimbal assembly (including the gimbal structure and nose portion) make the interface unstable and generate a strong or even a sustained slider (or even HGA) vibration. The vibration will result in slider flying high for some period of time and than returning to normal fly height as the vibrations reduce below a threshold. This phenomenon is known as fly height hysteresis. When slider is flying higher than normal, the read/write performance is degraded. This problem is particularly egregious in the load/unload drives with smaller sliders like Femto. The cantilever design nose limiter extending from the flexure (referred to herein as flexure nose) above the slider provides an additional moment arm thereby increasing the HGA vibration which is not damped by smaller slider ABS. At high altitudes, after a disk contact, the slider may never comeback to normal fly height.
Background FIG. 1 shows a bottom view of a background head gimbal assembly (HGA) 100. HGA 100 includes a slider 129 and gimbal structure (e.g., flexure) 329. The gimbal structure 329 includes a flexure tongue 317, a front limiter bar 316, two flexible legs 342, electric leads 341 and a flexure nose limiter 210. As is known in the art, gimbal structure 329 is utilized to flexibly suspend the head supporting slider 129 from the load beam 128. In general, the flexibility of the gimbal structure allows the slider 129 to remain flexible while flying above the disk 115. In so doing, the slider 129 will maintain a correct attitude over the disk 115 allowing the head 220 (of FIG. 1) to remain in correct alignment with the disk 115 such that the read/write capabilities of the head 220 remain constant.
Flexure nose limiter 210 is utilized during unload times of the disk drive. That is, when the electrical lead suspension (ELS) 127 is moved to a secure off-disk location on L/UL ramp 197 during non-operation, the flexure nose limiter 210 is utilized in conjunction with a staging platform to reduce unwanted motion of the gimbal structure 329. For example, on a HDD having a plurality of ELS 127, and therefore a plurality of HGA 100, during the unload state there is a need to support the gimbal structure 329 such that the sliders will not contact each other during movement of the HDD, or when the HDD experiences a shock event. By utilizing a staging platform having intimate contact with the flexure nose limiter 210, and a front limiter 315 contact with the front limiter bar 316, the deleterious movement of the gimbal structure 329 during unload times is greatly reduced. The front limiter 315, the flexure nose limiter 210 and its associated staging platform (L/UL ramp 197) are well known in the art.
Referring again to background FIG. 1, a narrow width long window 270 is provided for termination of the electric leads 341 to the slider. After solder termination of the electric leads 341 to the slider these leads are practically rigid due to very small free length left. Major portion of these electric leads 341 near the slider is held rigidly attached to the stainless steel layer. Also, the flexure nose limiter 210 is small in width at the base and has a very small window 275 in stainless steel. Very small window 275 is separated from narrow width long window 270 by rigid bridge 230. Rigid bridge 230 comprises the stainless steel layer. This background configuration of the gimbal and nose design has a rigid connection between the slider and flexure gimbal and nose that results in amplifying the vibration amplitude caused by disturbances like slider to disk contact, into a resonance resulting in sustained abnormal flying of the slider.
With reference still to background FIG. 1, in one embodiment, during normal operation of the HDD, operational disturbances such as contact between the slider 129 and the disk 115 occur. As stated herein, one of the major problems with the background is intermittent contact of the slider 129 inducing vibrations on the flexure nose limiter 210 of the HGA 100. For example, when the slider 129 encounters the magnetic media or disk 115. That is, when the slider 129 contacts the disk 115, dynamic coupling between the flexure nose limiter 210 and the slider 129 provides an unstable interface as well as generating a strong or even a sustained vibration resonance at the flexure nose limiter 210.
This problem is even more pronounced since the flexure nose limiter 210 extending from the gimbal structure 329 provides an additional moment to the HGA 100 thereby increasing the vibration characteristics between the slider 129 and the gimbal structure 329. In other words, when the flexure nose limiter 210 begins to vibrate the additional mass and moment help maintain the vibration (e.g., reaching a harmonic state) of the flexure nose limiter 210. Generally, a very small energy can keep the vibration sustained for a prolonged length of time such that the read/write capabilities and the interface reliability are significantly impacted. That is, the flexure nose limiter 210 vibration will result in slider 129 flying high thereby degrading read/write performance, or resulting in the slider/disk interface failure. It also limits the ability to achieve the lower flying height required for higher recording density.
One effective method of resolving the flexure nose vibration resonance includes adding of external viscoelastic dampening material in the flexure nose and the flexure gimbal areas of the suspension. However, although the addition of damping material at the point of high strain is an effective solution, it also adds additional cost and time to the manufacturing of the suspension.